This invention relates to a programmable controller, specially to the monitor display system of input/output data and timer/counter data.
As it is widely known, in many general programmable controller, an input/output (I/O) status display having display lamps to correspond with each of terminals, is provided on the terminal board of I/O circuit to joint external I/O devices, where in actual use it is so arranged that the logical state of any I/O signal which is to be input to or output from each of the terminals will be displayed by flashing of a display lamp which corresponds to the terminal. Thus, the user can visually confirm on the display the status of the ever-changing I/O signal while the programmable controller is in the operating condition.
But, it also includes a problem that, when I/O equipment is to provide the above I/O status display, it will mean an increase of the total costs. In addition, it is seen relatively often in the actual use of programmable controllers, that the above I/O equipment is built into the control panel of the device, making the above I/O status display, and thus the I/O status, difficult to see.